EMORY OAK IN SOUTHERN ARIZONA. 5 



CHARACTERISTICS OF THE TREE. 

 FORM. 



Emory oak varies in form and size and character of stand more 

 than any other oaks in its range, according to its situation; its 

 leaf and bark forms, however, are fairly constant. This silvical 

 variation is very pronounced in the extreme forms, although the 

 gradation between types may be very slight. In a general way 

 there are characteristic bottom stands and slope stands, as exem- 

 plified in the Garces National Forest, and these may be subdivided 

 according to location. For the bottom stands there are: (1) Those 

 of the broad open valleys at elevations of from 3,500 to 4,500 feet; 

 (2) those in narrower valleys at from 4,500 to 5,500 feet; and (3) 

 those on slope bases and bench lands at elevations of from 3,800 

 to 5,500 feet. There are two subdivisions of the slope stands: 

 (1) Those on north and east slopes at elevations of from 5,000 to 

 7,000 feet and (2) those on south and west slopes at from 5,000 

 to 7,000 feet. 



In the broad, open valleys the tree reaches its maximum devel- 

 opment, with breast-high diameters of from 2 to 3 feet and a total 

 height of from 60 to 70 feet. Indeed, some of the trees in these 

 situations are 3^ or 4 feet in diameter and 80 feet tall. 1 In these 

 large trees the clear length may be from 10 to 30 feet. The shape 

 of the crown varies according to the age of the tree, being a tall 

 and regular oblong in the younger veterans and a broad, flat oval in 

 the old ones. One strong characteristic is the flat plane in which the 

 leaves and twigs grow on the branches. This peculiar growth is not 

 particularly noticeable in standing trees, but shows very plainly in 

 one that has been felled. 



In the narrow valleys the trees are much smaller, with a breast-high 

 diameter of from 6 to 8 inches and a height of 20 or 30 feet, though 

 occasionally they may be from 12 to 18 inches in diameter and as 

 much as 40 feet high. Here the clear length varies from 1 to 15 

 feet, and the crown is a narrow oblong, with a tendency, however, 

 toward the oval in the older trees. Not only do the leaves and 

 twigs grow in horizontal planes, even more markedly than in the 

 trees of the broad valleys, but the branches themselves are nearly 

 at right angles with the stem. 



In the slope stands the individual trees are shorter and have a 

 wider crown in proportion to their height. The stands on the north 

 and east slopes are from two to three times as dense as those on 

 south and west slopes. 



1 Dr. Edgar Alexander Mearns states, in Bulletin 56, U. S. National Museum, "Mammals of the Mex- 

 ican Boundary of the United States," that he has seen trees in the neighborhood of the Garces National 

 Forest which are about 100 feet high. 



